Web Server Tuning

Your web server needs to be tuned before going into production. The standard configuration included with the Apache distribution (or with our OS software package) is not optimised for high load web sites and you will therefore need to modify it. It is particularly important to configure the mpm_common worker module for production use. Be sure to read and understand the documentation for this module and then continue to these more general Apache performance guides:

• http://httpd.apache.org/docs/2.2/misc/perf-tuning.html

• http://www.devside.net/articles/apache-performance-tuning

The Apache worker is set at compile time. Thus, if you have compiled it from source, check your build (configure) options to be sure the multi-threaded worker is selected. If you have installed Apache from RPM/DEB packages, you can usually use rpm -qa | grep -i apache or dpkg -l "*apache*mpm" to make sure that the high speed worker is being used.

This example shows how to configure the Apache worker for production use.

# worker MPM
<IfModule worker.c>
# We could increase ServerLimit to 64 and ThreadLimit/MaxClients to 8192,
# but be aware of the OOM of Death!!

# initial number of server processes to start
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#startservers
StartServers         3
ServerLimit          32

# minimum number of worker threads which are kept spare
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#minsparethreads
MinSpareThreads     512

# maximum number of worker threads which are kept spare
http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#maxsparethreads
MaxSpareThreads     1024

# upper limit on the configurable number of threads per child process
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#threadlimit
ThreadLimit         4096

# maximum number of simultaneous client connections
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#maxclients
MaxClients         4096

# number of worker threads created by each child process
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#threadsperchild
ThreadsPerChild     128

# maximum number of requests a server process serves
# http://httpd.apache.org/docs/2.2/mod/mpm_common.html

#maxrequestsperchild
MaxRequestsPerChild  10000
</IfModule>      

Make sure that you have a good understanding of the MaxKeepAliveRequests and KeepAliveTimeout parameters. The following values:

MaxKeepAliveRequests 1000
KeepAliveTimeout 5

work well in many production sites today. However, your needs may be different and you should therefore be careful when setting these parameters.